1. Field of the Invention
The present invention relates to a receiver for a real time locating system (RTLS) using active radio frequency identification (RFID) and a method of receiving a signal in the RTLS, and more particularly, to a technique for removing interference of a heterogeneous signal of the same frequency band from an RTLS reader. Particularly, the present invention relates to realization of an adaptive transversal filter (ATF) for reducing the impossibility or errors of communication caused by interference between heterogeneous signals of the same frequency band of 2.4 GHz in the structure of an RTLS receiver.
2. Discussion of Related Art
Referring FIG. 1A, the available frequency band of an RTLS is a 2.4 GHz industrial, scientific and medical (ISM) frequency band. This frequency band is the same as that used in wireless local area network (WLAN), Bluetooth, or the like, and is used by many wireless instruments. In particular, an RTLS reader, a receiver of the RTLS requires constant power, which imposes restrictions on installation conditions of the RTLS reader. Generally, various wireless instruments coexist around a place where the constant power is supplied. This causes problems of a decrease in performance, information loss caused by errors, etc. due to an influence of reception of an unnecessary signal.
A transmission signal transmitted from an RTLS tag is modulated using direct sequence spread spectrum (DSSS) modulation. Referring to FIG. 1B, the DSSS modulation has high resistance to signal interference due to a processing gain. However, in the case of relatively high signal interference as in FIG. 1C, its influence renders location of the RTLS tag impossible or causes a great error.